1. Great sex before bed that puts you right to sleep.

"Cocka-by" - "cocka" replaces "lulla" in Lullaby.'

2. As similarly explained in Wikipedia: A Cockaby (wk: Lullaby) is a soothing "sextivity", usually done with compliant participants before they go to sleep, with the intention of speeding that process; after explosion of great orgasm

Wikipedia (for Lullaby): A lullaby is a soothing song, usually sung to young children before they go to sleep, with the intention of speeding that process.