hazel: [OE] Hazel is a very ancient tree-name. It can be traced right back to Indo-European *kosolos or *koselos, which also produced French coudrier and Welsh collen. Its Germanic descendant was *khasalaz, from which come German hasel, Dutch hazel-, and Swedish and Danish hassel as well as English hazel. The earliest known use of the word to describe the colour of eyes comes in Shakespeare’s Romeo and Juliet 1592: ‘Thou wilt quarrel with a man for cracking nuts, having no other reason, but thou hast hazel eyes’.
hazel (n.)
Old English hæsl, hæsel, from Proto-Germanic *hasalaz (cognates: Old Norse hasl, Middle Dutch hasel, German hasel), from PIE *koselo- "hazel" (cognates: Latin corulus, Old Irish coll "hazel"). Shakespeare ("Romeo and Juliet," 1592) was first to use it (in print) in the sense of "reddish-brown color of eyes" (in reference to the color of ripe hazel-nuts), when Mercutio accuses Benvolio:
Thou wilt quarrell with a man for cracking Nuts, hauing no reason, but because thou hast hasell eyes.