dam
n.
1
"water barrier," early 14c., probably from Old Norse dammr or Middle Dutch dam, both from Proto-Germanic *dammaz (cognates: Old Frisian damm, German Damm), which is of unknown origin.
2
"animal mother," c.1300, variant of dame, q.v., also originally used, like that word, for "lady, mother;" but meanings diverged into separate spellings by 16c.
v.
late 15c., from dam, n.1. Related: Dammed; damming.