A friend has a rowan tree, also called the mountain ash, in her garden, which set me wondering (a) if I could get hold of some rowanberry jelly, just to try; and (b) where name rowan comes from.
The answer to (a) is no, unless I make myself or pay an exorbitant delivery charge. The answer to (b) is that it's probably named for the bright red colour of its berries. The immediate origin seems to be Scandinavian (the Swedish is rönn) but there is a suggestion that it may go back ro the Proto-Indo-European root *ruidh-, 'red'.
This is the PIE colour word we are most confident of, because words that can be traced back to it, with meanings related to 'redness', are found in so many branches of the Indo-European language family. Some examples are English ruddy, Sanskrit rudhira, Polish rudy, Welsh rhudd, Lithuanian raudona, Latin rufus, Greek erythros.
Other English cognates include red, of course; rust, russet, rouge, roan and ruby. A particularly interesting one is ruddock - Britain's favourite bird, known today as the robin, but called in Old English rudduc, 'little red'. Here's a later example I found in the Middle English Compendium (sote = 'sweet' and the two thrushes are the song and the missel.)
How sote this seson is..The thrustelis & the thrusshis..The ruddok & the Goldfynch.
Picture credit: George Chernilevsky, Vinnytsia, Ukraine, Rowan Berries, on Wikimedia, Licensed under Creative Commons.