Does the 고사 (姑捨) in 고사하고 mean "to throw away one's mother-in-law"?

 ANSWER: No.

The Sino-Korean word for "anti-aircraft gun" is 고사포 (高射砲), which literally means "high (高) shooting (射) cannon (砲)." But "setting that aside," this morning, after I had looked up 고사포 in my Korean-English dictionary to confirm the Chinese characters used in it, I noticed the word 고사(姑捨)하고 and became curious about the Chinese characters used in the word. 

The word 고사(姑捨)하고 means "setting aside," but the Chinese characters used for 고사 are the characters for "mother-in-law" (姑) and "to throw away" (捨). That didn't make sense to me. In other words, I couldn't understand how "throwing away one's mother-in-law" could mean "setting aside." So, I looked up the Chinese character for "mother-in-law" and noticed, for the first time, that it can also mean 잠시, which means "a short while" or "a little while."

So, the 고사 (姑捨) in 고사하고 does not literally mean "to throw away one's mother-in-law." It literally means "to throw away for a little while," which can translate as "to set aside for a little while."