What does earn-in or back-in in finance mean?

Any idea?

“Earn-in” I’m not familiar, but earn-out is common term in M&A. An earn-out is usually structured as a payment to seller from buyer some time after the closing of the deal, based upon the performance of the subject company.

I’ve seen the term earn-in in oil and gas whereby the purchaser acquires a working interest in an asset or project and is required to also pay for a portion of the sellers capital commitments (the earn-in) to secure the working interest.