Despite the name and flavour text, the grenade's legendary ability bears no resemblence to Overwatch's Widowmaker's Venom Mine, which unlike the missile projectiles fired by this grenade mod, is instead a proximity mine that, when triggered, deals damage over time.
The flavor text is literally translated as "to life, to death". As a French expression, however, it is taken to mean "'til death do us part" or "united forever".
The name Widowmaker is a double entendre which also refers to the widow mines in Starcraft 2 that have a very strong resemblence to the special effect animation when the mines are triggered as this grenade mod. The pun intended is that the Widowmaker mod makes widow mines.