Hm, I haven't really thought about it. It is quite informal. The context of "bailing on" a party is the typical usage, eg.
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People used to say eg 'I'm sorry I had to bail out of your party', but the 'out' gradually stopped being used, and the 'of' became 'on'.
CliveI remember when people (kids) began to stop saying 'bail out' and started to just say 'bail'. Then 'on' gradually crept in.Fascinating story. I quite interested in. Why is it going like this?
CliveBut my memories are just mine.You mean it is not going like this now? (the kids' language development process)