From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
Lao Chu (ラオ チュウ, Rao Chū; FUNimation "Mr. Lao") is an elderly man and a skilled martial artist.
Lao Chu appeared in "A Girl Named Lime". He was a shopkeeper and the grandfather of Lime, a young girl Son Gohan met prior to the Cell Games. When Lime started a rumor that Future Cell was near the secret hideout that was built as protection, her grandfather came to her aid. He beat up Borbonne's men with ease and was then opposed by Tao, who proved to be just a little too much for him. He was then saved by Gohan from a Super Dodon Wave. Son Goku arrived and talked with Lao Chu like they knew each other. Amazingly, this elderly martial artist was well aware of Goku and Gohan's super powers and knew beforehand that they would be entering the Cell Games. Even more startling was the fact he knew Cell's first form objective was to absorb Human energy and even stated that Cell was much weaker back then. It is never known how this wise old man knew about Goku or Cell's evolution being that the Earthlings just knew him as a monster.
Lao Chu strongly resembled Mutaito, who once trained with Goku via time travel. He also resembled Fighter 83, who lost to Goku in the Elimination Round of the 21st Tenkaichi Tournament. Lime mentioned that he once fought in the Tenkaichi Tournament. As he made no appearances in the manga, it leaves this as a mystery. His name was only revealed in the English dubs. In the Japanese dub, Lime just called him Gramps.