From Middle English lullen, lollen. Cognate with Scots lul, lule, loll (“to lull, put to sleep, howl, caterwaul”), Dutch lollen (“to sing badly, caterwaul”), Dutch lullen (“to chatter, prate, cheat, deceive”), Low German lullen (“to lull”), German lullen (“to lull”), Danish lulle (“to lull, sing to sleep”), Swedish lulla (“to lull”), Icelandic lulla (“to lull”). Originally, perhaps expressive in origin from la-la-la or lu-lu-lu sounds made in calming a child.
lull (plural lulls)
- A period of rest or soothing.
- (nautical) A period without waves or wind.
- (surfing) An extended pause between sets of waves.
- About 2 hours in, a long lull cleared everyone out, and then it started getting a little more consistent and pushing chest ta neck high — 808surfer.com forum 
- (transitive) To cause to rest by soothing influences; to compose; to calm; to soothe; to quiet.
- to lull him soft asleep
- Such sweet compulsion doth in music lie, / To lull the daughters of necessity.
- (intransitive) To become gradually calm; to subside; to cease or abate.
- The storm lulled.
- (To cause to rest): appease