Olentzero (Basque pronunciation: [olents̻eɾo], sometimes Olentzaro or Olantzaro) is a character in Basque Christmas tradition. According to Basque traditions Olentzero comes to town late at night on the 24th of December to drop off presents for children. In some places he arrives later, for example in Ochagavía – Otsagabia on the 27th and in Ermua on the 31st.
The name Olentzero appears in a number of variations: Onenzaro, Onentzaro, Olentzaro, Ononzaro, Orentzago and others. The earliest records give the name as Onentzaro and the name is most likely composed of two elements, on "good" plus a genitive plural ending and the suffix -zaro which in Basque denotes a season (compare words like haurtzaro "childhood"), so "time of the good ones" literally. This suggests a derivation similar to the Spanish nochebuena, but the origin of Onentzaro, corresponding to the old feast of the winter solstice, is older than that of Christmas (which historically replaced the festival of Sol Invictus in 380 under Theodosius I in the Roman Empire).
Other theories of derivation exist but are not generally accepted:
In parts of Navarre this holiday is called xubilaro or subilaro from subil, the word for a Yule log plus the suffix -zaro. In parts of Lower Navarre the word suklaro is used, a contraction of sekularo. Sekularo has no clear etymology but is likely to be related to Latin saecularis.