Come-on and Come upon

Come-on noun - Something that persuades one to perform an action for pleasure or gain.

Come upon and come-on are semantically related. In some cases you can use "Come upon" instead a verb phrase "Come-on".

Come upon verb - Find unexpectedly.

Come-on and come upon are semantically related. Sometimes you can replace phrase "Come-on" with "Come upon", this terms are similar.