rear its head

ひらがなタイムズの３月号（２００９）Japanese Overseasのコーナーに記事にあった文です。
Life there was not immediately easy for him and homesickness began to rear its head.
私の知っている "rear" ではこの文の意味には全く合いません。辞書で "rear" の意味を丁寧に読んでもピッタリするのはありません。　色々な辞書をしつこく調べたら "rear its head" もしくは "rear its ugly head" と言うイデオムであることが分かりました。
Cambridge Dictionary of American Idioms: to become a problem that has to be dealt with It was in the 1970s that the problem of violent soccer fans first reared its head in Britain.
World Wide Words:
[Q] From Arthur Hart: “So many bad things today seem to be rearing their ugly heads! What was the first thing that reared its ugly head, and who first turned this colourfully descriptive phrase?”
[A] This has indeed become a cliché. It refers to something that has made an unwelcome appearance or has become a troublesome subject that requires attention. This, for example, appeared in the Irish Independent on 5 July 2007: “Critics have noted the short battery life, an issue that has already reared its ugly head for the iPod.”
World Wide Wordsの説明はこの後も長々と続きますので興味のある方はhttp://www.worldwidewords.org/qa/qa-rea2.htmに行って読んで下さい。