Gung-ho (on) is an expression that originated in the military and is used to describe someone who is enthusiastic and eager to take on a task. It is derived from the Chinese phrase 'Kung Ho', which translates to 'work together'. The crossword solutions for this term are INTO and SOLD, both of which have four letters. INTO refers to the willingness to get involved in something, while SOLD is a reference to the commitment and dedication required to complete a task. Together, these two words capture the spirit of the phrase Gung-ho (on).