What is the meaning of -ko?

Locative singular suffix.

Noun-forming suffix with various functions.

1. related to, near

   related to, near

   Forms words expressing a hit or strike

   Forms future participles.

   forms diminutive nouns

   Turns a clause interrogative. It is appended to the element of the clause that is questioned most. English equivalents include the normal ways of forming an interrogative statement without using an interrogative pronoun, such as the verb "do", inversion of the word order and intonation.

   In indirect questions, -ko/-kö appended to the verb corresponds to the conjunctions if and whether in English.

   With the particle -han/-hän attached to the topic of discussion, it expresses "I wonder if".

   With the negative verb (en, et, ei, emme, ette, eivät) and the particle -han/-hän, expresses "I suppose".

   In a question with an interrogative word.

   forms the accusative case

   a feminine singular suffix (often used with a collective sense)

   First-person singular ergative enclitic pronoun; I

   First-person singular possessive marker; my

   alternative form of -k

   you (familiar second person singualr and plural)

   augmentative suffix; used to form nouns meaning a larger form of something.

   Used to form a nominalised and superlative form of verbs.

   diminutive suffix for neuter nouns; may cause various vowel shifts

   Makes a clause interrogative; marks yes-no questions.

   Rōmaji transcription of こ

   added to neuter nouns to form a diminutive

   diminutive suffix for neuter nouns. May cause various vowel shifts

   Suffix appended to words to create a masculine noun, most likely to make diminutive. Usually used to make names, or nicknames denoting a negative feature.

   diminutive suffix for neuter nouns

   ku class_(XVII) relative marker, where

   Source: wiktionary.org