JLPT2 G2 S7 F1615
來 is a depiction of a barley plant, emphasizing the rows of pendent fruits of grain concealed in husks (compare 米). 夂 leg/foot pointed downward was added to yield a new character, 麥, meaning "come" → plant come from Central Asia. However, the meanings of 麥 and 來 were eventually inverted, so that 麥/麦 now means *barley* and 來/来 come; bring about → *wheat*; *oats*; *rye* → *grain*.
[Full Kanji Etymology List]