I think your Pearl Jam story is the one that Vedder told to a credulous journo who swallowed it hook, line and sinker. The singer himself admitted to Rolling Stone
that is was "total bull****".
The truth, mentioned in the article, is somewhat more prosaic: they were Christened "Pearl" by bassist Jeff Ament & added the second word after a Neil Young gig were he played several 15-20 minute jams.
Of band omitted from your list the godlike Thin White Rope
were named after a William Burroughs's description of semen from The Naked Lunch
, perennial CW favs The Decemberists
take theirs from the 1825 abortive Decembrist Uprising in Russia &, sadly, rumours Bury's finest Elbow
took their moniker from nickname of Pakistan off-spinner Saeed Ajmal are apocryphal.They actually used a line from Dennis Potter's telly series The Singing Dectective
, wherein Michael Gambon says "elbow" is the most sensuous word in English because of the way it feels to say.