-unculus

Meaning

1. morphemesuffixSuffix forming diminutive forms of nouns, ultimately an extended form of -ulus.
   avus (“grandfather”) → avunculus (“uncle”)
   rāna (“frog”) → rānunculus (“tadpole”)

Origins

Uncommon variant of -culus. The great majority of diminutives that end in the letters -unculus were not formed using this suffix; rather, they were formed by adding the diminutive suffix -culus to the stems of third-declension nouns with nominative singular forms ending in -ō and oblique stems ending in -in- or -ōn- (such as homunculus (from homō, homin- + -culus) and sermunculus (from sermō, sermōn- + -culus)). In these, the ending -unculus results from alteration of the vowel before the stem-final n to u due to either regular phonetic sound change (in the case of original *ōn or *on) or analogy. Rebracketing of -culus in the above class of words may be the source of the words where -unculus appears to be used as an independent suffix; alternatively, some words that appear synchronically to have this suffix may have actually been formed originally on an unattested n-stem base (such as avunculus).