The complementizer after verbs of speaking, thinking and perception is ma, with the variants kuma and kumâ. Thus, it is not identical to the element ki 'that', which introduces other clauses (e.g. subject clauses). Historically, (ku)ma is linked to
old Ptg. coma 'as'. However, it can also be linked to kuma of Guinea-Bissau Kriyol, which has the meanings 'say', 'that' (after verbs of speaking and thinking) and 'as' and which, on its part, is probably related to Mandinka kuma, which, as a noun, means 'speech' and, as a verb, 'say'.
Source: Lang et al. 2012
Source: Brüser et al. 2002: s.v. algen