So... Dinah Drake. Me likey this new person.
Head canon time: Due to DBI (Damnit Barry Interference), Dinah Drake gets stranded in the past, meets and falls in love with a young Quentin Lance, and gives birth to Laurel and Sara. I mean, we know that Mrs. Lance's name was indeed Dinah, and the complexion and hair color are similar
Further explanation:
In the CW Arrowverse, we've been recently introduced to a new character to take on the mantle of the Black Canary, a former Central City cop named Dinah Drake. Unlike Laurel, who used a mechanical device to generate her Canary Cry, Dinah was caught in the Star Labs explosion and has a metahuman Canary Cry not unlike Earth 2 Laurel.
The reason why Oliver chose to recruit Dinah Drake was because of her abilities, but the final seal was when she told him her name (she had been living under an alias). As we know, Laurel Lance's full name is Dinah Laurel Lance, and she was named after her mother.
Now, with The Flash and the Legends of Tomorrow, we have temporal shenanigans aplenty, and with Damien Darkh, Malcolm Merlyn, and Eobard Thawne traveling through time, I posit the following:
At some point, Ollie and crew will be helping out with the Legion of Doom, and Dinah Drake will get stranded in the past, where she will meet, fall in love with, and marry Quentin Lance, eventually giving birth to two girls named Sara and Laurel.
Dinah takes the unusual approach of naming her first child after herself to close the time loop, ensuring that things take place just as they are supposed to happen.
It also explains why Sara's mother was so insistent that Sara did not die on the Queen's Gambit and why she was the least angry with Oliver upon his rescue. She already knows how things play out.
