Other forms: inundated, inundating, inundates
To inundate is to flood — or to overwhelm somebody with more than they can handle. Water, or email.
The literal sense is a real flood, and inundated land is under water. The figurative sense is now far commoner, and being inundated with calls, applications or complaints means the volume defeated whoever was answering. It is nearly always passive. The noun inundation belongs mostly to the literal sense, and swamped and deluged do the figurative job with the same watery image.
Inundate is a wave coming in. Latin unda meant a wave and inundāre to flood or overflow, so a person inundated with requests is standing under one.
Proto-Indo-European
*wed-
Latin
inundātus
English, today
inundate
Built from
1623; Latin inundātus, the perfect passive participle of inundō (“to flood, overflow”) (see -ate), from in- + undō (“to overflow, wave”), from unda (“wave”) + -ō.
Etymology from Wiktionary, CC BY-SA