Check in and Fall in

Check in verb - Announce one's arrival, e.g. at hotels or airports.

Fall in and check in are semantically related In some cases you can use "Fall in" instead a verb "Check in".

Fall in verb - Break down, literally or metaphorically.

Check in and fall in are semantically related in advance topic. Sometimes you can use "Check in" instead a verb "Fall in", if it concerns topics such as come to a destination.