To better understand underrepresented undergraduates' motivation for pursuing their major, we examined undergraduates' articulated explanations for their major choice and its association with their motivational beliefs within an introductory chemistry course. Students' (n=503, 68% female, 56% First-Generation College-Going, 34% Hispanic) open-ended explanations for their major choice was examined a) by examining prevalent content themes, and b) by examining linguistic features of their written responses (word count, use of affective words). Undergraduates most frequently referenced occupation-related and enjoyment-related reasons for their major choice. Undergraduates in Life science-related majors that mentioned occupation-related reasons also reported lower levels of interest in Chemistry. We also found a positive association between students' surveyed motivational beliefs in Chemistry and the length of their major choice explanations.