Thinko

"Thinko" is a computer science slang term for a mistake in a program's actual design, instead of a technical mistake when writing the program out or when running it, or for a bug caused by such a mistake.

The word "thinko" is a portmanteau between the verb "think" (implying that the mistake was already present when the programmer first even thought the design through) and the earlier slang term "typo", short for "typographical error". (The obvious back-formation to "thinkographical error" is of course nonsensical – "cognitive error" would be better.)