-y

From Middle English -y, -i, from Old English -iġ (“-y, -ic”, suffix), from Proto-West Germanic *-g, from Proto-Germanic *-īgaz (“-y, -ic”), from Proto-Indo-European *-kos, *-ikos, *-iḱos (“-y, -ic”).

Cognate with Scots -ie (“-y”), West Frisian -ich (“-y”), Dutch -ig (“-y”), Low German -ig (“-y”), German -ig (“-y”), Swedish -ig (“-y”), Gothic -𐌹𐌲𐍃 (-igs, “-y”), Latin -icus (“-y, -ic”), Ancient Greek -ικός (-ikós), Sanskrit -इक (-ika). Doublet of -ac and -ic.

Proto-Germanic *-j-, *-ij-

Proto-West Germanic *-i, *-ī

Old English -iġ

Middle English -y

English -y

Cognate with Scots -ie, being inherited directly from the same source Middle English -ie, -i, from Old English -iġ (“-ie, -y”, diminutive suffix), possibly from Proto-West Germanic *-ij-, *-j- (diminutive suffix).

Not related with Dutch -je, -ie, regional Low German -je, which are from Proto-West Germanic *-ikīn (English -kin as in lambkin), nor with German -i, which is from Proto-West Germanic *-īn (English -en as in maiden). The vowel /i/ has an onomatopoeic quality to it, which may reinforce its occurrence in diminutives.

From Middle English -y, -ie, -ee, -e, from Anglo-Norman and Middle French -ie and -é, from Latin -ia, -ium, -tās, Ancient Greek -ίᾱ (-íā), -ειᾰ (-eiă), -ιον (-ion).

Cognate (as far as Latin -ia is involved) with German -ei and Dutch -ij.

Inherited from Middle English -y, -ie, for earlier -ien, from the Old English weak class 2 infinitival suffix -ian, -iġan, by syncope from earlier *-ōjan, North Sea Germanic form of Proto-West Germanic *-ōn, from Proto-Germanic *-ōną; reinforced by the suffix -ian, -ġan in Old English verbs of weak class 1 with roots ending in -r (and the exceptional strong class 6 verb swerian). Compare -en (infinitive ending).