I've always been under the impression that foutre is as rude in French as words such shit or fuck but in a Le Monde video titled Viol: pourquoi le cerveau empêche certaines victimes de réagir on youtube one of the interviewees uses the phrase « ça fout la trouille » (7:35) when asked about her experience with assault, which I thought would be quite a formal situation. Is foutre used here for emphasis or can it be used somewhat formally in certain circumstances?
" foutre ", as a name or subtantive, means the result of ejaculation, that is sperm.
You can find it in old populaire saying, such as " Foutre Dieu " ( Holy Shit ), a " Jean foutre " ( a ne'er do well ) or alone, " Foutre " ( Fuck ).
Foutre as a verb means familarly : to do. It is much less vulgar, just a little popular.
Qu'est-ce que tu fous? has the same meaning as " What are you doing?" ( qu'est-ce que tu fais? ) , only you would say it only to someone you know well.
In all its acceptations this verb is considered to be at least coarse.
As it refers to sex it is considered obscene, indecent. ("trivial" in French).
trivial (TLFi) − LEXICOGR. Marque stylistique appliquée à des mots de niveaux de langue familière ou populaire, que la norme socio-culturelle condamne comme ayant des connotations indécentes, grossières ou obscènes (d'apr. Ling. 1972).
This concerns the first group of meanings (derived figurative meanings from the basic concept).
As concerns the other groups of meanings it is considered to be vulgar.
In the expression « ça fout la trouille » its sense is "mettre".
(TLFi) D.− Vulg. [Avec un compl. prép. désignant un état phys. ou psychol.]
- [Le compl. est un subst.] Mettre (quelqu'un) dans tel ou tel état.
♦ Il m'a foutu en boule; ça le fout en colère.
"Mettre la trouille" or "donner la trouille" is not found in Google Books. However, "donner la peur" and the less frequent "mettre la peur" are found and this says that these two verbs can be used with "trouille", which is nothing else than an exact colloquial synonym of "peur". (ngram)
In this particular sense careful speakers replace "foutre" by the euphemistic "ficher³" (TLFi), which has come into use as an express replacement, but which is still a colloquial term. See for instance this page of examples; as these writings are for a good number of them from the last decade, it can be inferred that the verb "foutre" is still far from being legitimized as a part of the sound and solid vocabulary of French.
The common expression ça fout la trouille is colloquial but not obscene or rude.
It doesn't use the vulgar original meaning of the verb foutre, which traces back from the Latin futuere (literally: to fuck), but the softer slang usage of the same verb that means to do, to make, to put. The verb ficher can be used as a softer replacement for foutre, e.g.: Fiche-moi la paix ! vs Fous-moi la paix ! for "Give me a break!"
Trouille is also a slang word for peur so a non slang equivalent of this sentence is ça fait peur.
See also this reply about "slangness gradation".