sawn
"four-letter word" is another phrase meaning "curse word, so the phrase might mean that boobies is not a scientific word for breasts, but it's not considered vulgar, either.
A four letter word starting with the letter a is able.
Jack.
A four letter word for 'in addition to' is also.
rate
knot
The word heart is another four-letter word that is related to your circulatory system.
chum
over
swap
halt
Mind.
shop
well
sere
rife