The Isnag are a small ethnolinguistic group in the mountains of Apayao. They are one of several mountain peoples who were never subdued in nearly 350 years of Spanish rule. The Isnag live in settlements along the river, but move up into the hills to tend their farms during certain seasons of the year. Each village along the river is marked by tall coconut palms towering above it. Most villages are quite small. Despite all the space at their disposal, the people still build their houses rather close together, both for protection and companionship.
Like most other Filipinos, the Isnag are of Malay-type ancestry. Little is known about where they came from before they settled in Apayao, or when they came. Various names have been used to designate the Isnag. They are called los Apayaos or los Mandayas in Spanish references. Los Apayaos refer tot he river along whose banks the people live; and los Mandayas is related to an Isnag word meaning "upstream".
The word Isnag probably came from an Ilocano word meaning "from Tineg," a town and a river in Abra. The word later came to mean "enemy' and was later discarded, and this mountain people came to be known by their neighbors as "Isnag". Isnag and Apayao are alternative terms that refer to the inhabitants of the Apayao in what used to be part of Mountain Province before it was patritioned into the five provinces of Benguet, Kalinga, Apayao, Mountain Province and Bontoc.
Very little is known about how the Isnag lived before the Spaniards came to the Philippines. It is probable that they lived much as they do today, by hunting, fishing, and kaingin farming. That there was a direcr or indirect trade with China is evidenced by the Chinese jars, plates and beads that are prized possessions of many Isnag families.
Activities related to head taking occupied a large part of the time of Isnag men: learning the art of war, training the young men, making and repairing their weapons, and protecting their homes and families from attack. There were four major reasons why the men took heads: for religious reason, for prestige, as a qualification for marriage, and for revenge. After a number of battles before and after 1913, the Isnag were convinced that their spears were no-match for the "thundersticks" of the American soldiers. From that time on, the Isnag lived as a comparatively peaceful people.
The religious of the Isnag is animalistic; their traditional religious beliefs were concerned with their relationship with a great number and variety of spirits. Two elements usually present in religions were largely lacking in that of the Isnag: belief in a supreme being, and a serious attempt to explain the nature of the universe.
Beauty seems to have very little premium, if at all, in Isnag customs and traditions with respect to courtship and marriage. Consideration of beauty is not what propels Isnag swains toward the choice of a mate but rather a woman's capacity to work. Health and strength are developed more important. Amazon-like women have decided edge over the fragile ones in the contest for affections of man. Such seems to be the sad lot of the Isnag women to work on the kaingins (swidden fields).
A man who happens to own a large kaingin is constrained to indulge in polygamy, which is duly sanctioned by their traditions. However, it is rarely practiced as the Isnag resort to polygamy not for pleasure but to acquire additional help.
The Isnag generally abhor marriage between cousins or kin. Such marriages occur sometimes only because of such factors as scarcity of women, difficulty of travel and enmity with the other tribes.
Divorce is not entirely alien to the Isnag, which invariably reflects the flexibility of their characte. But the principal reason for divorce, as the Igorot, is failure to bear children. Educated Isnag women reject the custom of having them work on the farm. Thus, they prefer to marry into another ethnic group, prefirably the Ilocanos who are reputed for their industriousness.
Encyclopedia of the Filipino People.