bod.

From Middle Welsh bot, from Proto-Brythonic *bod, from Proto-Celtic *butā (cf. Cornish bos, Breton bout), from Proto-Indo-European *bʰuH- (“to be, become”); all the b- initial forms are from the same root. The vowel-initial forms as well as sy(dd) are from Proto-Indo-European *h₁es- (“to be”). The present-progressive forms with yd- (ydwyf, etc.), and hence the colloquial present-affirmative forms with d- (dw, etc.), are from the affirmative particle yd. Colloquial affirmative forms with r- (rwyt, roeddwn, etc.) are from the affirmative particle yr. Colloquial negative forms with d- (dydw, does, doeddwn, etc.) are from the negative particle nid. The third-person singular present mae originally meant ‘here is’ and is from the same source as yma (“here”) plus Proto-Celtic *esti. The third-person plural maent (colloquial maen) is derived from the singular by adding the third-person plural verb ending -nt. Counterfactual forms such as petaswn and taswn are from univerbation with pe (“if”) + yd (affirmative particle).