Why is "limerick" spelled incorrectly in this book?

This book has over 650 limericks, best described this way...Perchance, might you find time to peruse / my book of lim-ricks while on your cruise? / Most are clean…none obscene. / Most are gentle…none mean… / and all are intended to amuse. The word “limerick” is purposely spelled incorrectly and you will discover why in Chapter 1...”The Anatomy of a Lim-rick”. Other chapters bear names like... (2) Lawyers; (3) Death & Dying; (3) Animals; (4) “Sandusky-gate”; (5) Geriatrics; (6) Irish Culture; (7) Politics & Historical Events; (8) 50’s and 60’s music; (9) Food Prep & Menus; (10) Adventures of Jack & Jill; (11) A Farewell Roast & Toast; (12) Honoring the Twelve Months-of the-Year; (13) Lim-ricks that Ask Questions; (14) The Three R’s; (15) Flotsam & Jetsam; and (16) Miscellaneous. The (almost) 150 lim-ricks, in the last two mentioned chapters, defy easy categorization. Here are some examples...Past performance is no guarantee / of future reliability. / Since his escapade / in his Escalade / Tiger’s had no “MAJOR” victory. I suffer from chronic repition / trying to maser basic diction. If I had a hammer /I’d destroy my stammer / and be free to speak without friction.