Synonyms of privately

3 Syllables
stealthily, ourselves, privily, secretly, alone, covertly, inwardly, aside
4 Syllables
insidiously, furtively, internally, familiarly, personally
5 Syllables
surreptitiously, confidentially, clandestinely, intimately, unofficially, underhandedly
6 Syllables
conservatively, unobtrusively
8 Syllables
individualistically