In this chapter we are going to look at two pairs of cognate words Eng. patrimony ~ Sp. patrimonio and Eng. matrimony ~ Sp. matrimonio, as well as words that contain the Latin morphemes contained in these words: namely patr‑ ‘father’, matr‑ ‘mother’, and the ‘ending’ ‑mōn‑ĭ‑um. We will look first at the pair Eng. patrimony ~ Sp. patrimonio and then at the pair Eng. matrimony ~ Sp. matrimonio. Finally, we will explore the main words in English and Spanish in which we can recognize the Latin root patr‑, the root matr‑, and the main words with the ending Eng. ‑mony ~ Sp. ‑monio.
Let us start by saying something about the cognate ending ‑mony/‑monio. These are descendants of a Latin suffix whose meaning is not apparent today and was not apparent either in the days of Classical Latin, and thus it is presumptuous to call it a suffix, as opposed to an ending. The Spanish version is pronounced [‑ˈmo.ni̯o], with the word’s main stress falling on the suffix’s first syllable. The English ending ‑mony is pronounced in two somewhat different ways. In American English, it is pronounced [ˌmoʊ̯.ni], with secondary stress on the first syllable, whereas in Standard British English, that same syllable is unstressed and thus the vowel gets reduced to what’s known as a schwa vowel sound [mə.ni] (cf. Part I, Chapter 7, §126.96.36.199).
The English ending ‑mony and its Spanish cognate ‑monio are the modern reflexes of the Latin suffix or ending ‑mōn‑ĭ‑(um), where the ‑um part is the inflection, which changed from one case wordform to another. The ending was the same in the nominative and accusative cases and is was added typically to nouns to produce resulting is an abstract noun, sort of like what ‑hood does in English in a word like personhood, derived from the noun person. The meaning of the resulting noun referred to the action, state or condition of whatever the root indicates. Primarily, Latin ‑mōn‑ĭ‑um formed collective nouns and nouns that designated legal status or obligation. Latin did not have many words with this ending and not many have been passed on to English or Spanish either, as we shall see since the main ones will be covered in this chapter.
Latin -mōn‑ĭ‑um is obviously a compound ending, consisting of the suffix ‑mōn‑ and the suffix ‑ĭ‑ that was originally an adjectival suffix. This blend of suffixes is thought to go all the way back to the Proto-Indo-European ancestor language and to have been rather opaque as to its meaning by the days of Classical Latin. The Latin suffix ‑mōn‑ has been reconstructed as coming from Proto-Indo-European root *‑mō, *‑mn̥, or *‑mḗn, three different ablaut variants of the same root, that originally created agent nouns from verbs. The original suffix should had a short ‑o‑ vowel like its Greek cognate shows, not a long ‑ō‑ like in Latin. It is thought that the lengthening of the vowel in Latin came through contamination from the lengthened o in the nominative of ancient words with this suffix which resulted from the loss of the ‑n‑ in the nominative case. Thus, we have a common Latin word like sermō ‘conversation, speech, etc.’, whose genitive form was sermōnis (ser‑mōn‑is) and its regular stem sermōn‑ (ser‑mōn‑), the source of Eng. sermon ~ Sp. sermón. This Latin noun has been reconstructed as coming from Proto-Indo-European root *ser‑ that meant something ‘to bind together, to thread’. By the time this and other Proto-Indo-European words containing this suffix got to Latin, the suffix had ceased to be productive or transparent to speakers, however. Another Latin word that comes from the same Proto-Indo-European root *ser‑ is sors (genitive: sortis, accusative: sortem) ‘fate’, source of Sp. suerte ‘luck; fate’.
The nominative plural wordform of the Latin ‘suffix’ -mōn‑ĭ‑um is -mōn‑ĭ‑a, which is also the same in the nominative and in the accusative. The suffix -mōn‑ĭ‑a was used in Latin to create (singular) abstract nouns typically from adjectives, such as sanctimōnia ‘virtuousness’, derived from the adjective sanctus ‘holy’ (cf. Eng. sanctimony and sanctimonious); acrimōnia ‘pungency; austerity’, from the adjective ācer ‘sour; harsh’ (cf. Eng. acrimony); and parcimōnia or parsimōnia ‘thrift’, from parcus ‘sparing, slight’ (cf. Eng. parsimony).
Ancient Greek had a cognate of the suffix -mōn‑, with a short o, as in the original source, which was found in a number of words that Latin borrowed from Greek, which were later borrowed by English and Spanish. One of them was Gk. δαίμων (daímōn) ‘god, divine power, protective spirit (equivalent to Lat. genius), etc.’, a noun derived by means of this suffix from the verb δαίομαι (daíomai) ‘to divide’. Latin borrowed the word δαίμων (daímōn) from Greek as daemon or dæmon (genitive daemŏnis; stem: daemŏn‑), which Christian Church writers came to use with the meaning ‘an evil spirit, demon’. In Medieval Latin, the spelling changed to dēmōn. This is the source of Eng. demon, a word borrowed from Latin around the year 1200.
Later, Latin also borrowed from Greek the noun daemŏnĭum ‘a lesser divinity, a little spirit, especially an evil spirit, demon’. It comes from Ancient Greek δαιμόνιον (daimónion), whose main meaning was ‘the divine power, deity, divinity’, but it was used with the meaning ‘an inferior divine being, demon’. This noun is derived from the adjective δαιμόνῐος (daimónios) ‘extraordinary, divine’, derived from the noun δαίμων (daímōn) by means of the -ῐ‑(ος) (‑i‑os) adjectival suffix. This is the source of Sp. demonio. Because of their slightly different sources, we say that Eng. demon and Sp. demonio are paronyms, not full cognates (cf. Part I, Chapter 1).
Another Greek noun that had this ‑mon‑ suffix in its inception was ἁρμονία (harmonía). Its meaning was something like ‘means of joining, fastening, etc.’ and in the context of music, ‘stringing, method of stringing, musical scale’ (GEL). Latin borrowed this word as harmŏnĭa ‘an agreement of sounds, consonance, concord, harmony’ (L&S), and this is the source of the cognates Sp. harmonía ~ Eng. harmony.
 In Ancient Greek, the noun δαίμων (daímōn) could be used interchangeably with θεός (theós) (as in theology), but when used together it typically referred to lower god than a θεός (theós).