Larkin makes use of some well-placed repetition and wordplay to emphasize one of the poem's key ideas: the inescapability and degrading qualities of work. Sounds fun, right? Larkin gets extra vocabulary bang for his buck by choosing, and in some cases repeating, words that have secondary functions beyond their primary meanings that help reinforce the ideas and images he wants us to consider.
Title; Lines 1, 25: The title, and references to toads in poem itself, echo the term "toady": a person that is very servile to people in power—kind of like some people feel they have to behave with their bosses. So we get the sense of the slimy little creature that hops around in bogs and the slimy little creature we are forced to become, at times, for our jobs.
Lines 2, 25-26: Larkin repeats the word "squat" for a couple of reasons. We already talked about what an unpleasant word it is (see "Unpleasant Sights, Sounds, and Smells" for more on that aspect), but repeating the word also allows Larkin to make a subtle change between the word's first and second appearance. In line 2, the toad squats on the speaker's life. It is an external problem. In lines 25-26, something "toad-like" squats in the speaker as well. The ugliness of the word, and the ugliness of the work and obligation the toad represents, are internalized. It isn't just some unpleasant thing the speaker might be able to shoo away with a "pitchfork." It is an internal problem, an internal ugliness, as well. Yuck.
Lines 22-23: Any time a word is repeated in a quatrain, it's going to get some added attention. In the poem's sixth stanza, Larkin repeats the word "stuff." In line 25, the verb "stuff" is used in the very colloquial, modern, rough sense of, "Stuff your pension!" Go Phil! You tell 'em. In the following line, the noun "stuff" is used in a phrase echoing a line from Shakespeare's play The Tempest: "That's the stuff / That dreams are made on." Larkin forces us consider the modern era and the Renaissance era in the same moment. As a result, we get the sense that this struggle against a life overcome by meaningless work is an inescapable, universal struggle that has been going on for centuries. Let's take a break. Shmoop suddenly feels the need to go and stare into the abyss.