another think coming or another thing coming

And another think

by

An article from the New Statesman today included the passage:

If Rachel Reeves imagined her repeated insistence that Labour's "iron-clad" commitment to sound public finances would spare her the fate of Stafford Cripps, Jim Callaghan and Denis Healey, she had another thing coming.

I stopped reading after “she had another thing coming”. What was coming? A promotion? A cup of coffee? Surely what was meant was that her rumination would require further thought – she had another think coming. The Ngram view (for what that is worth) shows the ‘coming’ form taking off from around 2000 and becoming the more usual form today.

A chart showing the increase in usage of thing over think

It is a curious phrasing. The folksy etymology often attributed to American usage but one suspects that anyone who thinks that has another think coming.