Antonyms for the phrase "was pertinent" includes words like, "irrelevant," "unrelated," "unconnected," "immaterial," "inapplicable," and "unimportant." All of these words signify a lack of significance or relevance to the subject matter, rather than importance or pertinence. For example, a piece of information that is inapplicable or irrelevant to a discussion, would not be considered pertinent to the topic at hand. Conversely, information that is useful, relevant, and directly applicable to a discussion or problem would be considered pertinent. It is important to choose the correct antonym for "was pertinent" to ensure accuracy and clarity of communication.