Is (or was) “whow” really a word?
Certainly. For this they invented dictionaries, one of the best of which for finding out whether something once was a word is the OED:
whou, whough(e, whouh, whow(e, variants of how, howe int.1
- C. 1425 Quhow: see whew int.
- 1542 Udall Erasm. Apoph. 314 ― Whough, saieth he, half my brothers bodye is more then the whole.
- 1598 R. Bernard tr. Terence, Phormio ɪɪɪ. iii, ― How much money need you? speake. But thirtie poundes. Thirtie! Whow.
- 1615 Brathwait Strappado 129 ― Whou Billie whou, what faire has thou bin at?
- 1627 W. Hawkins Apollo Shroving ɪɪ. iv. 33 ― He answered me nothing but whough, pugh.
- 1815 Scott Guy M. xlv, ― ‘Eh whow! Eh whow!’ ejaculated the honest farmer, as he looked round upon his friend’s miserable apartment.
So † whowb(e (in quots. as sb.; cf. howbub, hubbub).
- 1600 W. Watson Decacordon ᴠɪɪ. x. (1602) 217 ― They hissed him out with whoubs & hoo-bubs.
- 1600 W. Watson Decacordon ɪx. viii. 327 [see how, howe int.1].
It used to be a word. It probably isn’t any longer: modulo the cited farmer’s ejaculation, it hasn’t been much seen in four centuries. It used to mean the same thing as did the word How! when uttered as an interjection.