noun
separate place; another place
Refers to a location distinct from the current or previously mentioned one. Often used when specifying a different venue or address.
会議は別所で行います。
The meeting will be held at a separate location.
荷物は別所に保管されています。
The luggage is stored in another place.
noun
newly cultivated land
Rare, historical term for land recently brought under cultivation. Not used in everyday modern Japanese.
古文書には、別所として新たに開墾された土地の記録が残っている。
Ancient documents contain records of land newly cultivated as 別所.
他所 means 'another place' in a general sense, often implying somewhere else or outside one's own group. 別所 is more neutral and simply indicates a different location.
Compound of 別 (separate) and 所 (place). The second sense 'newly cultivated land' is an archaic extension of the literal meaning.