A popular song of the time, which the cosmonauts had adopted as a private joke.
The cosmonauts jokingly called each other 'Lilies of the Valley', having parodied the love song, turning it into a drinking song.
Vesna (“spring”) was used as callsigns of radio stations in Moscow and Khabarovsk, operating on HF rather than VHF.
Zaria (“dawn”) was both the name of one of the mission communications systems, and used as callsigns for the ground stations. The Zaria communications system was designed by NII-695, led by their Chief Designer Yuriy Sergeyevich Bykov, who was present at the Zaria-1 ground station at the launch site.