I'm looking for a term in English to describe being so polite that one appears to be insincere.
This is a good page which may be helpful to you. My picks would be the following:
- smarmy: using societal constraints/rules (i.e. politeness) to passive-aggresively/non-confrontationally get one's way. That's my interpretation, but here's an article about it.
- oily/greasy: like a businessman or shopkeeper or something who dotes on clients/customers so heavily (and maybe crosses personal-space boundaries in so doing) that it's almost viscerally unpleasant.
- obsequious: I would say that obsequious is more subtle than the others, but again, that's my interpretation. Look for uses in books or something.
I disagree with the MacMillan page on the following points:
- 'Suave' I take to mean smooth, well-dressed, and having nice things, with no connotation of insincerity.
- 'Proper' I take to mean stiff or rigid politeness; again, not necessarily insincere (cranky people besotted with their rules can be sincere!)
I like unctuous...
unc·tu·ous [uhngk-choo-uhs] adjective 1. characterized by excessive piousness or moralistic fervor, especially in an affected manner; excessively smooth, suave, or smug.
1. Of, relating to, or characteristic of sugar or saccharin; sweet.
2. Having a cloyingly sweet attitude, tone, or character: a saccharine smile.
Literally, it is a chemical that is an artificial sweetener. Figuratively, it can be used to describe a person or action that is so sweet it seems to be artificial.
You haven't noted whether or not it is the speaker's intent to be insincere.
Along those lines, I would suggest that one could purposefully be overly polite - and when veiled in thick sarcasm, the speaker would certainly come across as insincere.
I would like to suggest "fulsome":
"Although the earliest use of fulsome (first recorded in the 13th century) was ‘generous or abundant’, this meaning is now regarded by some people as wrong. The correct meaning today is held to be ‘excessively complimentary or flattering’. However, the word is still often used in its original sense of ‘abundant’, especially in sentences such as she was fulsome in her praise for the people who organized it, and this use can give rise to ambiguity: for one speaker, fulsome praise may be a genuine compliment, whereas for others it will be interpreted as an insult."
Insincerity, whether it is purposeful or not does not matter people. The point is the person appears to be insincere due to exaggerated amount of politeness. Its unknown the person's reasons for the overkindliness.
Unctuous is the the best post thus far and smarmy is the next. Both, however, do not state whether the person appears insincere. Simply that the person is being overly polite.
I don't believe there is such a word as the question is asking for. Unctuous could be used like this to reach the same affect as the question asked: Their unctuous behavior made them appear insincere.
Charles Dickens created one of the best architypes for this behaviour in his book David Copperfield. His villainous, fawning character is "Uriah Heep".
Reading about Uriah Heep will give you great insight and vocabulary in the description of this character.