Sh’visa – rest, termination of a creative process, refraining from activities. Apparently with a “TAV” so could be Sh’vita – and probably related to the root verb SHABAT
Sh’vus (or Shvus)- (a) A Shvus is an action prohibited by the Chachamim on Shabbos or Yom Tov. The Torah states “… uva’Yom ha’Shevi’i Tishbos” — “… and you shall rest on the seventh day” (Shemos 23:12). The Rabanan understood this to apply even to actions that are not Melachos, and as a result they prohibited actions that would otherwise be permitted (see Shabbos 114b). The term “Shvus” is derived from the word “Tishbos” in the Pasuk. [Source: http://www.mail-archive.com/daf-background@shemayisrael.co.il/msg00074.html quoting “Background to the Daily Daf – http://www.dafyomi.co.il – on Beitzah 21 & 22)
Sh’vus D’Shvus – a situation where two rabbinic laws are in force simultaneously
Source: https://www.dafdigest.org/eiruvin/Eiruvin%20091.pdf
Mamash – (Mamish?) – I’m still trying to find if these are two different pronunications or two different words.
According to this page: http://www.mamash.org/pages/content/meditations.html, the word “Mamash” has no English translation, the closest thing being an exclamation point. I think the word “really” might be a loose translation. “The Kaballah Handbook” says that it is a word that embody levels of truth beyond metaphor or abstraction, that is literally and concretely true from the highest to the lowest of worlds. It goes on to provide possible translations: substance, matter, truly, literally.