The phrase "honest injun" is a derogatory term that has been historically used to question the integrity of Native Americans. Today, it is not considered an appropriate or acceptable term to use. Instead, there are many synonyms that can be used to convey the idea of honesty without resorting to stereotyping or offense. Some possible options include trustworthy, truthful, sincere, candid, and frank. Using these synonyms can help communicate the idea of honesty while avoiding negative connotations or hurtful language. It's important to be mindful of the impact of our words and strive to use language that is respectful and inclusive of all cultures and identities.