Not quite. They called them 'Muhammadans' because they initially thought that Muslims viewed him(Muhammad) the way they(Christians) did Jesus, with a bit of Mary thrown in. I say this because obviously the first two Christian sects to encounter the "little brother" of the Abrahamic faiths were Roman Catholics & Byzantine/Greek Orthodox, who as you know, use "worship" or revere Mary as a 'link' to Jesus and through Jesus, to God/YHWH/Allah.
Catholics have, and in some cases still do, get similar accusations by other Christians(read-as Protestants and Even-More-Than-Usual-Historically-Incompetent Christians who reject the Protestant label in favour of something nigh-hipster like, such as Latter-Day Saint or Jehovah's Witness) as worshiping Mary in the stead of God.