till the cows come home：很久，无限期
从前乳牛未经人工改造，每年都有不产奶时期。在产奶时期，它们乳房充盈，不挤奶会很不舒服，自然会主动回家给人挤奶；但是，在不产奶时期，要它们主动回家，真不知要等多久了。所以，till the cows come home有“很久”、“无限期”的意思。
:he is very long-winded and will keep on talking till the cows come home
他是个话篓子，会说个不停的。
holy cow: 对某事表示惊讶, 惊奇, 愤怒等.
"a friend of mine is in hollywood filming a movie this month." "holy cow, that must be so cool."
“我的一个朋友这个月正在好莱坞拍电影。”“天哪，这太酷了！”
as awkward as a cow on roller skates：非常笨拙，笨手笨脚.
the little girl was as awkward as a cow on roller skates when she first began riding her bicycle.
这个小女孩刚骑自行车的时候笨手笨脚