Origin: Germanic Old English prefix
Underscore has 5 different meanings across 2 categories:
a line drawn underneath (especially under written matter)
"She used her pen to underscore every important point in the contract before handing it back to me."
An underline; a line drawn or printed beneath text; the character _.
"She decided to underscore her signature on the contract before handing it back."
give extra weight to (a communication)
"Her gesture emphasized her words"
draw a line or lines underneath to call attention to
"The editor asked me to underscore the key statistics in bold so readers would immediately notice them."
To underline; to mark a line beneath text.
"The teacher used her red pen to underscore the key vocabulary words at the bottom of the page."