Uncle_sure

Removed by mod

No problem, I’m glad to have such a great discussion! By the way, English teachers in slavic countries like to teach very old phrases/memes. Like “raining cats and dogs” for the heavy rain, “wet blanket” for a grinch person. Also they can trying to tell something about cockney (which will never help students in real life) So it’s no wonder that some virtually non-existent russian memes could go into textbooks. But the “go to Riga” is not completely dead yet. Need to wait for a decade or two :)

By the way, the Riga sounds like “Ryga” in Belarusian. So this idiom should not have been outdated. Just a bit artificial. But to be artificial is okay if you want to avoid direct naming of unpleasant things. I believe that “travel to Riga”=“poyekhal rygat’”=“go puke” is a meme for a lot of native Russians around Saint Petersburg.
It’s totally ok that some teacher include that meme into their course. This is totally recognizable for a native speaker (like for me in my late thirties).

You will be really surprised how many local silly names exist for menstruation. “Red day of the calendar” - allusion on communist holidays. “Red army arrival day” - no explanation is needed. “Relatives from Krasnodar just come” - Krasnodar is literally “Red Gift”, so it’s obvious again. “The critical days”, “these days of the calendar”… I’ve heard all these variants in the wild by my own ears.

P.S accidentally found an independent confirmation regarding Riga https://translate.google.com/?sl=auto&tl=en&text=https%3A%2F%2Fcyberleninka.ru%2Farticle%2Fn%2Fbolezni-i-ih-frazeologicheskie-evfemisticheskie-nominatsii-v-russkom-angliyskom-nemetskom-frantsuzskom-yazykah &op=translate

In Russian “to throw up” sounds like "rygat’ ". So the story and the usage looks plausible (especially for some of Sant Petersburg folks).