No, please, I couldn’t possibly. Sorry. No, no, no. Thank you. Sorry.
(Rei mo sugireba burei ni naru;
“Even politeness, when overdone, becomes insolence”)
An overabundance of manners and deference becomes rude. Even for something as valuable, and as fundamental to the proper functioning of society, as good manners, there can be too much of a good thing.
We begin with the noun 礼 (rei), “ceremony,” “reward,” “thanks,” “etiquette.” This is followed by emphatic particle も (mo), here serving as “even,” and then the verb 過ぎる (sugiru), “to [sur]pass,” in a pseudo-conjunctive form* and taking the hypothetical suffix ば (ba), “if” or “when.” The following independent clause ends with the verb なる (naru), “to become,” in conclusive form. This is preceded by the directional particle に (ni), which tells us that what 礼 becomes is the noun 無礼 (burei), “rude[ness],” literally just a negation of 礼.
The first image that popped into my head was an error: I imagined someone deliberately and mockingly using the forms of politeness inappropriately for the social context to give offense. But my sources paint a picture based on the practical downsides of extreme obsequiousness: even when no offense is intended, it can be a pain having someone checking in on your mood constantly, asking how you want things done, and so on.
*The classical base form of the verb is 過ぐ (sugu); 過ぎ (sugi) was both the imperfective and conjunctive forms. In this case, it acts as the imperfective and takes the passive particle る (ru), which in turn takes conjunctive form as れ (re).
(“Ano kouhai wa… kidzukai dekiru no wa ii nda kedo… komakai tokoro made nando mo kikareru no wa chotto…. Honto, rei mo sugireba burei ni naru yo ne.”)
[“That underclassman… it’s good that they know to take other people’s feelings into consideration… but getting asked about every little thing is a bit…. Being too polite is a kind of being rude, you know?”]