[refset]

According to Wikipedia:

> The original name SEQUEL, which is widely regarded as a pun on QUEL, the query language of Ingres, was later changed to SQL (dropping the vowels) because "SEQUEL" was a trademark of the UK-based Hawker Siddeley Dynamics Engineering Limited company. The label SQL later became the acronym for Structured Query Language.

[mannyv]

I heard that a long time ago as well. It's a successor to QUEL, so obviously the successor to quel is sequel.

[bch]

> regarded as a pun on QUEL, the query language of Ingres

Indeed Postgres, too, is a pun on Ingres itself (post-Ingres).