lay it on v.
1. in senses of communication.
(a) to charge excessively.
(b) [mid-19C+] to exaggerate; to make an excessive fuss.
(c) [1910s+] (orig. US) to criticize, to berate.
(d) [1930s–70s] (US black) to seek a verbal or physical confrontation, to hit.
(e) [1950s+] to inform, to pass on information.
2. [1930s+] (US) to act or work efficiently or energetically.
3. [1970s] (US black) to slap someone’s hand in greeting.