This is hopefully a specifically US thing, some companies' HR departments are extremely risk averse and will likely interpret that as you were in prison or rehab for six months.

I once, as an intern, had an HR assistant bring my application for a permanent position back to me because she wanted an explanation for why I was unemployed between June and August of the previous year (a year in which I was enrolled at a university.) I explained that I was in school and most companies don't hire people for only 3 months over the summer so I spent that time learning a programming language. She walked away looking annoyed.

Honestly, would have put 'Student at Blah' during those three months from there on.