Negation is a cornerstone of human language and one of the few universals found in all languages. Without negation, neither categorization nor efficient communication would be possible. Languages, however, differ remarkably in how they express negation. It is yet widely unknown how the way negation is marked influences the acquisition process of first language learners. Here, we investigate whether universal or language-specific cues are more relevant for the acquisition process. We test to what extent frequency and salience features (morphosyntactic boundedness, position of the negation marker, allomorphy) influence the acquisition of negation. We use naturalistic longitudinal data from 17 children (age 24-36 months) learning nine typologically maximally diverse languages spoken in very diverse cultural contexts ranging from western urban to subsistence farming: Chintang, English, Indonesian, Japanese, Qaqet, Russian, Sesotho, Turkish, and Yucatec Mayan. Distributional analyses show that the amount and type of input of negation that children hear vary considerably across cultures. Despite significant differences in the input that children receive, we observe a universal pattern in the acquisition of negation: Children transition from relatively easy and salient free negators to less salient bound negator morphemes in their use of negation. Our results show that frequency and morphosyntactic boundedness explain the development of flexibility in the acquisition of negation across all of the nine languages. We further find that the developmental path is shaped by the interaction between frequency and language-specific parameters of salience that are contingent on grammatical features of negation marking in different languages, such as the position of the negation marker and allomorphic variation. Our language-specific findings highlight cross-linguistic variation, which reflects cross-cultural differences in the amount of input of negative utterances children receive. Taken together, this study provides cross-linguistic evidence for the acquisition of negation and emphasizes the interplay of universal and language-specific factors in the acquisition process.