Thor's father, Odin, gets talked about a lot in both the MCU and Marvel Comics, but he's not the only parent of the God of Thunder. In fact, a revelation about Thor's love for his mother in the comics adds even more depth to one truly gut-wrenching MCU scene.
Thor Odinson's parentage is more than a little convoluted. His father is most definitely Odin, the All-Father, and the powerful ruler of Asgard, but it's the identity of his mother where things get tricky. Growing up, the young Thunderer believed that the goddess Frigga was his mother, as she was Odin's wife. It wasn't until thousands of years later that Thor's mother was technically of Earth, an earth goddess (and elder god) named Gaea, chosen by Odin to bond Thor to Midgard. Yet, even that revelation was thrown into doubt in Marvel Comics when the Phoenix Force claimed Odin had lied about Jord, and had actually laid with Firehair, the Phoenix's first human avatar.
Thor's First Word Proved His Love For His Adopted Mother
In truth, Jord was Thor's birth mother, but the Phoenix resurrected the infant after he was killed by the king of the Frost Giants. Yet, neither the elder god or the cosmic entity were Thor's true mother as shown in Thor Volume 6 #17, by Donny Cates and Michele Bandini. As a child the Odinson's first word was "mother" and he spoke it to Frigga, the woman who raised him, loved him, and treated him as her own even while knowing the truth.
This new dimension of Thor's parentage doesn't negate Frigga's role as his mother. In fact, it strengthens it and adds an even deeper meaning to scenes like we see in Avengers: Endgame. After time traveling to the past, Thor is once again confronted with Frigga knowing how she will die and unable to save her. Much like the scene in Thor #17, his mother offer him the comfort he needs to go on, even while knowing that truth of what awful things might soon transpire.
When the young Thunderer spoke the word "mother," he meant it for Frigga. In both the comics and movies she is able to put aside her own emotions to offer comfort to Thor, proving that it's not blood that defines motherhood but love.