Contrary to what might be expected, Dexys Midnight Runners is consistently spelled without an apostrophe. The word Dexy, in this case, comes from a colloquialism of dextroamphetamine or purple hearts, a type of amphetamine diet pill that was a popular "upper" drug with England's Northern Soul scene in the 1960s.
Discussion about the capitalization of "Come On Eileen".
Dexys Midnight Runners (currently officially Dexys, their common nickname; sometimes styled with and sometimes without an apostrophe)) are an English pop band with soul influences, who achieved their major success in the early to mid-1980s. They are best known in the UK for their songs "Come On Eileen" and "Geno", both of which peaked at No. 1 on the UK Singles Chart, as well as six other top-20 singles.
During the late 1970s and early 1980s, Dexys (no apostrophe) went through numerous personnel changes over the course of three albums and thirteen singles, with only singer/songwriter/co-founder Kevin Rowland remaining in the band through all of the transitions and only Rowland and "Big" Jim Paterson (trombone) appearing on all of the albums. By 1985, the band consisted only of Rowland and long-standing members Helen O'Hara (violin) and Billy Adams (guitar). The band broke up in 1987, with Rowland becoming a solo artist. After two failed restart attempts, Dexys was reformed by Rowland in 2003 with new members, as well as a few returning members from the band's original lineup (known as Dexys Mark I). Dexys released their fourth album in 2012 and a fifth followed in 2016.