Where does “[[ocainn]], [[acainn]], [[ocaind]]” come from?

[[ocainn]], [[acainn]], [[ocaind]] (Middle Irish) comes from Old Irish ocunn.

Ancestry of “[[ocainn]], [[acainn]], [[ocaind]]”, step by step

Step	Language	Word	Meaning
1	Old Irish	ocunn	—

[[ocainn]], [[acainn]], [[ocaind]] — Etymology, Origin & Word History | Etymology Explorer