Bang pong is Klingon for a pet name -- a term of endearment used between romantic partners. They are used only in private, and are generally not known to anyone outside the couple. These are highly variable and different from couple to couple, but most often are formed by taking a food, weapon, or body part and adding the suffix -oy (e.g., chatlhoy, yanoy, 'uSoy).
Because bang pong are only used amongst parmaqqay, outsiders should not use them; this would be offensive, but it is not so much taboo as it is childish and insulting. Because bang pongmey are highly variable and secret, it is easy for a foreigner to accidently sound like that are erroneously using one; it is best to avoid the -oy suffix and to be very careful when using objects as metaphors.