There is provided an ecommerce method and system to generate a data dictionary for searching data items stored in a database. In one embodiment, the system comprises a candidate list generator module to generate a list of keywords from search query information and generate a set of token pairs including a keyword from the list of keywords and a token, the token being a synonym of the keyword. Demand information retrieved from query logs maintained for user-provided query entries is used to apply candidate selection rules to token pairs. The system also comprises a validation module and a data dictionary module to receive validated token pairs as entries in a vocabulary.