Is whow a word?

According to this chart describing an extension of 5W1H, the word how originates from the word whow which means “how much”.

I can’t find any references to such a word on the Internet. Is (or was) whow really a word? If not, where do you think the author of the chart got his information from?

Here is the chart (Japanese only): <http://homepage2.nifty.com/thinking-way-8W1H/8W1H(A4).pdf>

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.