Privily means secretly, in old use. Sent privily, privily informed, meet privily.
It belongs to the Bible and to older legal English, and privately has entirely replaced it. It is worth knowing for reading rather than for writing. The privy behind it means private, and survives in the Privy Council and in privy to a secret.
1adverbprivilySecretly, in old use.
“The king's messenger was sent privily by night, so that no one would learn of the plan.”
privily is a manner.
Middle English prively, from privy, from Old French prive, from Latin privatus, private.
Middle English
prively
English, today
privily
From Middle English prively; equivalent to privy + ly.
Etymology from Wiktionary, CC BY-SA