Correct spelling for the English word "co stumer" is [kˈə͡ʊ stjˈuːmə], [kˈəʊ stjˈuːmə], [k_ˈəʊ s_t_j_ˈuː_m_ə] (IPA phonetic alphabet).
The word "costumer" is derived from the Middle English word "custumer", which is a variant of the word "customer".
The term "customer" has a Latin origin, coming from the Latin word "cūstum" meaning "custom" or "habit". In Medieval Latin, the word "custumarius" referred to a person who had the legal right to use a particular facility or to demand certain services or products.
Over time, the term "customer" evolved to refer to someone who purchases goods or services. Similarly, "costumer" refers to an individual or business that specializes in providing costumes.