Gentle caressing usually by repetitive hand strokes usually on the back. This is common for kids whilst being tucked to sleep and helps them doze off, but it is not uncommon in adults too. Lala is a swahili word which means to sleep and hence the light massage is related to dozing off.
Fiance: Oi thigh lala now.
Fiancee: But I want lala
Fiance: No, its not your turn. DO IT NOW WIFE.