I was reading the novel "Krabat" and came across the following sentences:
»Ja«, sagte Lobosch, »heuer zum letzten Mal. Denn nun bin ich hier Lehrjunge auf der Mühle.« Das sagte er voller Stolz, und die Mühlknappen dachten sich ihr's dabei.«
The bit that's confusing me is that last clause, "… und die Mühlknappen dachten sich ihr's dabei." I found a website that lists all the archaisms or otherwise strange idioms in this book and it lists that clause as being equivalent to "und die Mühlknappen dachten sich ihre Antwort darauf." So my understanding is that "ihr's," a contraction of "ihr es," is here an abbreviation of "ihre Antwort darauf," but I don't understand how exactly you get from one to the other.