आदरार्थे भवच्छब्दः

व्याकरणम्

निष्पत्तिः - भा (दीप्तौ) “डवतुः” (उ० १-६३) (वाचस्पत्ये, कल्पद्रुमे)
व्युत्पत्तिः - भातीति भवान्

कोशकराः

भवत्
mfn. (-वान्-वती-वत्) Thou; but used as a respectful term of address, as Sir or Lord, and governing the verb in the third person.
Wilson

Bavat {%(II) pron. (f. ती)%} The respectable pronoun translatable by ‘your worship, your honour, you’ (used for the second personal pronoun but with the third person of the verb),
LR Vaidya

एवं शब्दसागरः, शब्दार्थकौस्तुभः, Monier Williams, Lanman, Capeller, Apte.

प्रयोगालोकनम्

kaTha AraNyaka (veda): The devas feared him & humbly addressed him as “bhavAn” (Sir KA 2.100)mANikkavAchakar (9th century tamil shaiva saint): You, whom the vedas call “ayyA” (sir), oh, deep, broad & subtle one!