Do Russians still say "зонтик/ зонтики"? This was the word I learned for "umbrella" (many years ago).
Interestingly, the word зонтик is a loan word, it was formed by corrupting the German word Sonntuch (a piece of fabric protecting agains the sun), Initially, зонтик derived from зонтух wasn't perceived as a noun with the diminutive suffix -ик. It didn't happen until decades after the word was borrowed into Russian. But once people had started thinking of it as a diminutive form, they naturally coined a new word зонт which is mostly used in formal situations (e.g. in sales jargon).
And from Russian the word was borrowed into Finnish (Häme dialect) as "sontikka".
Yep, it's common to use these words, but the formal way is to say зонт/зонты.