snow under
snow under {v.}
1. To cover over with snow.
The doghouse was snowed under during the blizzard.
2. {informal}
To give so much of something that it cannot be taken care of; to weigh down by so much of something that' you cannot do anything about it. — Usually used in the passive.
The factory received so many orders that it was snowed under with work.
The disabled girl was snowed under with Christmas letters.
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Source: A Dictionary of American Idioms