"large, conical heap of stone," especially of the type common in Scotland and Wales and also found elsewhere in Britain, 1530s, from Scottish carne, akin to Gaelic carn "heap of stones, rocky hill" and Gaulish karnon "horn," perhaps from PIE *ker-n- "highest part of the body, horn," thus "tip, peak" (see horn (n.)).
late 14c., "small portable vessel (originally made of horn) for holding ink," from ink (n.) + horn (n.). Used attributively from 1540s ("Soche are your Ynkehorne termes," John Bale) as an adjective for things (especially vocabulary) supposed to be beloved by scribblers, pedants, and bookworms. An Old English word for the thing was blæchorn.
The term "Hornblende" is an old German name for any dark, prismatic crystal found with metallic ores but containing no valuable metal (the word "Blende" indicates "a deceiver") [Herbert Bucksch, "Dictionary Geotechnical Engineering," 1995]