Is it necessary to utter the word "zakat" when giving it to those who are deserving?

The recipients of zakat are legally defined in Surah At-Tawbah/60. The zakat giver is not obliged to inform the recipient that it is zakat. Some Maliki and Shafi'i scholars disliked this, and it is the apparent view of Imam Ahmad, unless the recipient is someone who does not accept zakat, in which case it is obligatory to inform them.