Though I called you “My lord,” you’ve no reason for pride:
For so to your slaves I have often replied.

[Cum voco te dominum, noli tibi, Cinna, placere:
Saepe etiam servum sic resaluto tuum.]

Martial (AD c.39-c.103) Spanish Roman poet, satirist, epigrammatist [Marcus Valerius Martialis]

Epigrams [Epigrammata], Book 5, epigram 57 (5.57) (AD 90) [tr. Pott & Wright (1921)]
    (Source)

(Source (Latin)). Alternate translations:

When "Sir" I call you, be not pleased; for know,
Cinna, I often call your servant so.
[tr. Wright (1663)]

When I call you "My lord," do not be vain, Cinna. I often return your slave's salutation in a similar way.
[tr. Bohn's Classical (1897)]

When I call you "master" don't pride yourself, Cinna. I often return even your slave's greeting so.
[tr. Ker (1919)]

When I call you "lord," don't get conceited. I often return your slave's greeting too in that way.
[tr. Shackleton Bailey (1993)]

I call you "Boss"? Don't show wild joy.
That's what I call my slaves' head boy.
[tr. Wills (2007)]

When I call you "lord," don't swagger, Cinna. Why?
I often give your slave the same reply.
[tr. McLean (2014)]

When I call you "Boss," Cinna, don't be so pleased with yourself; I often reply that way when your slave says hello, even.
[tr. Nisbet (2015)]

Variation:
Though I do "Sir" thee, be not vain, I pray:
I "Sir" my monkey Jacko every day.
-- Cyrus Redding, "N. M. Mag., 1828"