cosyn

From Old French cosin (and feminine cosine), inherited from Latin cōnsobrīnus.

cosyn (plural cosyns)

A member of one's family; one's partner, relative or their partner:
1. One's progeny; those who descend from one's lineage.
2. A nibling (niece or nephew); a child of one's brother or sister
3. One's direct cousin; a child of one's aunt or uncle.
4. (rare) Something bearing similarity to something else.

“cǒsī̆n(e, cọ̄sī̆n(e, n.”, in MED Online, Ann Arbor, Mich.: University of Michigan, 2007, retrieved 30 November 2018.

caws (“cheese”) +‎ -yn (diminutive suffix).

cosyn m (plural cosynnau)

(countable) a cheese
- 2021, Cathi McGill, Het Wellt a Welis: Blwyddyn Gron yn Astwrias, Carreg Gwalch, page 30:
  Yn ardal Gamonéu a bwlch Covadonga, uwchlaw'r llynnoedd, cwrddais i â gwraig oedd yn ei hwythdegau bryd hynny, yn byw mewn caban heb ddŵr na thrydan, ffynnon o flaen y drws a thân yn llosgi'n barhaol o dan simnai fawr. Ar y silffoedd o garreg, caws. Cosyn ar ôl cosyn yn aeddfedu yn y mwg.
  In the Gamonéu and Covadonga pass region, above the lakes, I met a woman who was in her eighties at the time, living in a cabin without water or electricity, a well in front of the door and a fire constantly burning under a large chimney. On the stone shelves, cheese. Cheese after cheese maturing in the smoke.

More information radical, soft ...

Mutated forms of *cosyn*
radical	soft	nasal	aspirate
cosyn	gosyn	nghosyn	chosyn

Note: Certain mutated forms of some words can never occur in standard Welsh.
All possible mutated forms are displayed for convenience.

Middle English