Discussion Forum—A Way with Words, a fun radio show and podcast about language

I used the word "tronch" in an email, intending to convey "a massive and somewhat chaotic bunch, or heap". ("a tronch of plots", describing ~3 dozen graphs made from one worksheet in an Excel file). Before I sent it, I checked to see if I had spelt the word correctly. I didn't find it in any regular online dictionary links, but was shocked when I was led to the Urban Dictionary, and learned some meanings that I can't put into a business email. (So, I rewrote the email.)

I checked online thesauri, and found bunch, mess, heap, and dozens more, but not tronch.

Answers.com has an entry about tranche in finance, which is a grouping of securities.

Is this a real word (meaning group)? Was I intending a valid useage? Did it indeed come from finance (which was then attributed to French)? Is it more general now than finance?

Thanks.