noun
Derogatory term for a stupid or foolish person. Strongly insulting; not for polite conversation.
あんなおたんちんに任せたら、仕事が台無しだ。
If you leave it to a blockhead like that, the work will be ruined.
noun
unpleasant customer
Archaic Kantō dialect term for a disagreeable or troublesome customer. Not used in modern standard Japanese.
江戸時代の商家では、おたんちんと呼ばれる客は厄介者だった。
In Edo-period merchant houses, customers called おたんちん were a nuisance.
The origin is uncertain. It may be a playful or sound-symbolic formation, possibly related to たんちん (simple-minded) with the honorific prefix お added ironically.