Lists as input

How do I pass list as an input? e.g.

-- function word(ext_word_list text DEFAULT NULL::text) returns text
SELECT faker.word('abcdef'); -- c
SELECT faker.word('abcdef'); -- a
SELECT faker.word('abcdef'); -- f
SELECT faker.word(ARRAY['foo', 'bar']::TEXT); -- {
SELECT faker.word(ARRAY['foo', 'bar']::TEXT); -- o

It seems to be a random choice from a CharArray.