maple tree genus name, from Latin acer, a word of uncertain origin, perhaps from PIE *ak- "be sharp" (see acro-) and so called for its pointed leaves.
There seem to have been two roots for "maple" in Indo-European; cognates of this one are said to include Old High German ahorn "maple," and there is a similar form in Greek akastos "maple," perhaps also Hittite hiqqar- "maple." De Vaan writes, "This may well be a non-PIE tree name which was borrowed into Greek and Latin."
