The title is taken from a book I've never read, by Sigmund Freud. Given the author and title... 地味 でしょう. Sounds rather serious.
Our conversation this week touched on manga, 敬語 (polite speech), parks, and—jokes.
Japanese has more than a few homophones (a survey in 2010 of the 2500 most widely used kanji in Asahi Shimbun noted that 106 kanji share the "コウ" 音読み), providing plenty of opportunities for puns:
Q: 固くて食べられないパンはなんですか (what type of bread is hard and inedible?)
A: フライパン (fry pan)
Freud would step in at this point to explain that パン is a loanword for "bread" (from Portuguese; those sailors got around back in the day) and "pan" (English). As puns go, it's nice and short.
Bad puns (and most are bad) are called 駄洒落 , an interesting compound of:
Paraphrasing Freud: sometimes kanji are just kanji, and you can't read a compound literally from its components. Yet: how did sprinkle (洒) and fall (落) come to mean "stylish," and then the not-quite-antonym "dumb joke?"
In the Heian Period (平安時代), poems with puns and double meanings were called 洒落, "witty". That term developed from 晒 (bleach, refine, expose to air) and 戯れ (play, joke); しゃれ is an ateji reading for 洒落. In parallel, お洒落 came to mean stylishly dressed, and the verb 洒落る supports both meanings.
When commoners tried their hand at 洒落, the nobles responded with the term 駄洒落 (not witty), a term that eventually took the meaning of "bad joke".
Another term for a "groaner" of a bad pun is 親父 ギャグ, literally "dad joke". We usually see those kanji in the opposite order, as in 父親 (father). Dad jokes appear to be worldwide: Indonesia ("lawakan om-om", "uncle jokes"); Germany ("flachwitze", "flat jokes") and so on.
美人を突き当たら、どうしたらいいですか。(if you collide with a beautiful woman, what should you do?)
ネタ refers to joke material. Despite the katakana, it's not a loanword, unless borrowing from Japanese itself counts: it's a reversal of 種, which means seed of a plant, or material for an article, or similar meanings along those lines. For this turnabout, jisho.org remarks tersely "kana reversed." No other entry has this note.
Japanese does have other examples of movement of syllables or phonemes within a word (known as metathesis). 雰囲気 (mood, ambience) has drifted to a ふいんき reading. Even 新しい, "new", had an older reading: 新たし.
下ネタ looks like "low humor", and this time our hunch is right: it means "dirty joke" or a more general "indecent topic." I won't provide examples here. A good place to find them is the Internet.
ネタバレ (or ネタばれ) is a spoiler for the end of a story or movie ("everyone is a robot" for example). ばれ comes from ばれる, an intransitive verb meaning to leak out or be revealed.
What's your favorite 駄洒落? More of a rhetorical question, as there's no comment section here. But you can tweet at @therealkurumi.
お疲れ様, thanks for reading!