> [doubts] the word is from the Welsh

Can't say I am surprised by that - the general picture is of an astonishing paucity of Welsh in the formation of the English language, given the history of these islands. I guess unlike the Saxon's knives and the spears of the other tribes, the Brythonic tribes were not remarkable for fighting prowess so their status was diminished; and their culture became sadly undervalued in the historical long term.

Does OED1 suggest an alternative etymology , Faldage?