Originally posted by Bruce Lindfield
Well I have read through the Milkowski bio a few times and this is part of a section which mentions how Jaco and his father Jack used to hang around together a lot when Jaco was young - so it says how they considered themselves to be a couple of Jazzbos! 
So my reading of it was that people saw them as big Jack and little Jack-O. So the derivation, was from Jocko, but nowhere does Milkowski say it was pronounced the same way and if it was, then why did Jaco bother to change the spelling? The only reason I can see for this, is to indicate how it was pronounced differently!!
Bruce, I'd say this passage from the Milkowski book explains the spelling change pretty clearly. You notice, not a hint of any change in pronunciation; it's about orthography, not sound:
"Apparently it wasn't until years later that he began spelling it J-a-c-o. As Gregory explains, "It was when he met Alex Darqui [the pianist who would later play on Jaco's 'Continuum']. Being French, Alex figured it was spelled like 'Paco.' One day he left a note with the name spelled J-a-c-o; Jaco must've liked it, because from that point on he started spelling it that way himself."
Occam's razor again: if the derivation of the name had been from his father Jack, surely he would have spelled it Jacko from the beginning, and his parents would not BOTH have said, on the record (see the Milkoski book), that the derivation was from Jocko Conlon. In the absence of any supporting evidence, it makes no sense to think that Jaco would initially spell his name Jocko but pronounce it Jacko. I grew up listening to basball games umpired by Jocko Conlon, and I can assure you his name was never pronounced Jacko.
Besides, as I said, I heard Jah-co (which, again, rhymes exactly with Jocko for most Americans) from his own mouth. You're still assuming that to go from Jocko to Jahco was a pronunciation change for Jaco; it may be for a Briton, but for an American, which Jaco of course was, it generally isn't. There isn't a shred of evidence in the Milkowski book that the pronunciation changed when the spelling did.
Also, Jacques does not rhyme with Jack for most US people; it rhymes with rock. Or Jock.
Believe it or not, we're saying almost the same thing--you just don't know it!
