It might be Turkic, given "kamşag" (kamshag) means "quake" in Old Turkic and Kamchatka region is often hit by earthquakes. The word and its verb form "kamşat-" (kamshat) appear several times in Orkhon Inscriptions.
The Orkhon Inscriptions were erected in honor of the two Turkic princes Kül Tegin and his brother Bilge Kagan and written by Yollug Tegin who was nephew of Bilge Kagan. The Inscriptions are two monoliths that contain long Old Turkic lines in Runic characters on three sides, and on one side (the western) the inscription is in Chinese. They are mostly about the social and political life of the Ancient Turks and their relations with the neighboring people mostly Ancient Chinese. They were deciphered by Danish philologist Vilhelm Thomsen in 1893.
As for the words, “Kamşag” which means “quake” or “shakiness” appears on the north side of Kul Tegin Inscription:
“Ėçim kagan ėli kamşag boltokınta bodun ėlig ėkegü boltokınta izgil bodun birle süŋüşdümiz”
I’m giving Talat Tekin’s English translation of the line from “A Grammar of Orkhon Turkic”, available online from here. (p.270)
“When the empire of my uncle, the kagan, became shaky and when the people and ruler were split into two parts, we fought against the İzgil people.”
And the verb form of the word appears on the east side of Bilge Kagan.
"Türk bodun adak kamşattı" meaning "The Turkish people tottered."
Given the nomadic nature of the Ancient Turks and their history in Siberia, I think the words might be related.