hailan is right.I also argee with Jeff. These words are from “Pilgrimage to the West” that is famous classical novel of China.They are all meaning the protagonist in the novel-Monkey King.It's something like jeu de mots or joke.

If you parse the sentence it means: 孙行者 Sun - the traveller 者行孙 - The traveller is Sun (the one who travels is Sun) 行者孙 -- The traveller Sun. The Monkey King was playing tricks on the monster to confuse it.

Hi Isabella! “孙行者” is 孙悟空's real name. He made up "者行孙” and "行者孙” himself. 孙行者、者行孙 and 行者孙 are all names. "孙行者" escaped from Qwedcxza's(the name of the monster) cltuth -- the bottle gourd. He thought if he used a fake name like "者姓孙", he wouldn't be sucked into the bottle gourd when he responded. It turned out that the bottle gourd would suck in anyone as long as he responds. It doesn't matter whether he uses a fake name or not. 者行孙 and 行者孙 claimed that they were 孙悟空's younger brother. In fact, they were the same person, because 孙悟空 wanted to trick the monsters. Hope it helps! :)

"孙行者" is one way for people to address Monkey King who is a main character in a Chinese mith novel <journey to the west>. "孙行者" was so naughty in one chapter of the novel that he asked one monster to call him "者行孙" and "行者孙" to make fool of the monster.

孙行者 者行孙 行者孙 孙悟空在<西游记>一个章节中使用的三个名字