[acorn] n [ME akern, fr. OE aecern; akin to OE aecer field, MHG ackeran acorns collectively, OIr airne sloe, Lith uoga berry] (bef. 12c): the nut of the oak usu. seated in or surrounded by a hard woody cupule of indurated bracts
ACORN
Meaning of ACORN in English
Merriam-Webster English vocab. Английский словарь Merriam Webster. 2012