I'm using this post to catalogue some of the more advanced terminal commands I use sometimes, but not often enough to commit to memory.

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grep -rnw ~/path/to/somewhere -e "pattern"

# -r or -R is recursive,
# -n is line number, and
# -w stands for match the whole word.
# i stands for ignore case (optional in your case).
# -l (lower-case L) can be added to just give the file name of matching files.