Where does “-u” come from?

-u (Old English) comes from Proto-West Germanic -u, from Veps -uz, from Sicilian -usu, from Latin -ōsus, from Old Latin -ōssus.

-u (Old English): ending used to form abstract nouns from...

Definitions

Step	Language	Word	Meaning
1	Proto-West Germanic	-u	Forms the
2	Veps	-uz	Forms nouns describing actions or results from verbs
3	Sicilian	-usu	ose; -ous
4	Latin	-ōsus	ose, -ous, -ful (full of or overly prone to)
5	Old Latin	-ōssus	—