What is the meaning of -iĉo?

of masculine sex

Traditionally male roots are used in a gender-neutral way, changing the meanings of patro from “father” to “parent”, frato from “brother” to “sibling”, etc. To make their male equivalents, -iĉo is applied. (patriĉo for “father”, fratiĉo for “brother”, etc.) This approach was the most common among early adopters of the suffix, and is heavily criticized by a significant number of speakers as being a too drastic reform of the language.

The suffix is used with traditionally male roots for purely stylistic symmetry with words that end in the feminine suffix -ino. (E.g. patriĉo and patrino for “father” and “mother”.) In this approach the form patriĉo is considered to be synonymous with the traditional patro (“father”).

The suffix is avoided with traditionally male roots, preserving their traditional meanings. It is only applied to root words that are not already explicitly male, e.g. junulo (“young person”) → junuliĉo (“young man”) and amiko (“friend”) → amikiĉo (“male friend”). This approach has become most common as usage of the suffix has spread.

↑ Wennergren, Bertilo (14 November 2020), “IĈ°”, in Plena Manlibro de Esperanta Gramatiko‎ (in Esperanto), retrieved 18 March 2021

Source: wiktionary.org