I'd like to correct the obviously popular but mistaken belief of many commenters that the Finnish name of the bug, leppäkerttu/leppäpirkko, has something to do with the tree leppä, alder.
Leppä in this case has nothing to do with alder. Instead both the tree and the beetle have been named for their red colouring (alder is rust red under it's bark). Leppä is simply an old word for blood.
Kerttu is a Finnish form of the German name Gertrud, which was popular all over Europe in the mediaval times since saint Gertrud was a very popular patron saint. Pirkko is likewise a Finnish form of Birgitta, another very popular (at least in nordic countries) medieval saint.
Therefore leppäkerttu means litarally blood Gertrud or bloody Gertrud and leppäpirkko means blood Birgitta or bloody Birgitta.
Funny thing is that neither of the saints died in a bloody way or was martyred at all.
@Kuutar
Some similar estonian words:
lepe, leping = a (blood-) contract
leppima = to agree, to sign a (blood-) contract
lepitama = to mediate a (blood-) contract
lepitamatu = (finnish) leppymätön = irreconcilable individual (do not even want a blood contract, what kind of a person is that?)
@ThorsomeTarmukas "leppymätön = irreconcilable" doesn't seem correct. Wiktionary suggests relentless or implacable, and I'd say that both of them are much more accurate translations.
If you're using Google Translate, you should know that it sometimes gives blatantly wrong translations, even if you're translating just a single word.
If lepitamatu means irreconcilable, I don't know why it would translate to leppymätön (leppyä = to relent), but that's what Google's translator says.
@mtomato
(estonian) ära leppima = to make up (/ resolve) one's quarrel with another party
(estonian) leppimatu = one who is adamantly unwilling to make up one's quarrel with another party
(estonian) lepitamatu = one who can not be mediated / persuaded to make up one's quarrel with another party
(finnish) leppymätön = relentless, implacable = (estonian) leppimatu
There is a fine distinction between leppimatu and lepitamatu, but to me it seems that at least leppimatu and leppymätön are of the same meaning. To relent is to come to an agreement with another party. To not relent, is to refuse agreement with another party.
irreconcilable = (of ideas or statements) so different from each other that they cannot be made compatible.
@Kuutar
Interesting; thanks!
Anyway, there seems to be a trend to have that beetle associated with women, something holy/magic, or both in many languages.
@ScottishHetalianCat is that a direct translation from Scottish Gaelic? Or just an English name given to it? If it's the second, I can understand why it's simple ;) It would be a back handed insult to the Brits.
@Iaraparka
Also in some older circles Alder Birgit. Leppäkerttu (Alder Gretel) and Leppäpirkko (Alder Birgit).
Bonus fact for you non-Fins, Alder part comes from the olden times when the word "leppä", which is now the name of alder trees in Finland, meant blood. And since chopped alder stumps and ladybugs are red...
Gretel, Kerttu, and Birgit, Pirkko, then, you may ask? I supposed they just wanted to use name instead of more anonymous lady, maiden or somesuch...
In Peru we talk in spanish so we also are insulting everyone every time we see one (but they're very rare) but in some spanish places it is called St. Antony's little cow
Leppä in this case has nothing to do with alder. Instead both the tree and the beetle have been named for their red colouring (alder is rust red under it's bark). Leppä is simply an old word for blood.
Kerttu is a Finnish form of the German name Gertrud, which was popular all over Europe in the mediaval times since saint Gertrud was a very popular patron saint. Pirkko is likewise a Finnish form of Birgitta, another very popular (at least in nordic countries) medieval saint.
Therefore leppäkerttu means litarally blood Gertrud or bloody Gertrud and leppäpirkko means blood Birgitta or bloody Birgitta.
Funny thing is that neither of the saints died in a bloody way or was martyred at all.
tl;dr
leppäkerttu = bloody Gertrud, leppäpirkko = bloody Birgitta