"Ate" and "Kuya" are addressed to the eldest among the siblings. The origin of these honorific titles are Chinese. The Chinese word for elder brother is "ko" and "a" modifies the word to mean "kin". Likewise, "Ate" is from "chi" and preceded by "a", this becomes "achi". In fact, this is how the Kapampangan (a major language in Central Luzon, not Tagalog) says it.
In some Tagalog regions and other parts of the north, the second eldest is called "diko" for males and "ditse" for females. In Chinese, "di" means "second". In some places, others pronounce this as "dete". "Sangko" means third in the heirarchy of birth. In Chinese, "sang" is "three" in the ordinal count.
Some stops here, but others go on to define their siblings accordingly. Thus, "sitse" for elder fourth sister and "siko" for elder fourth brother (Chinese "si", four) if another one comes along. As for the youngest, the Tagalog addresses them as "Totoy" for little boy, which in Chinese means "foolish son"; and "Nene" for little girl or "dull one" in Chinese. Totoy can become "utoy", "ato", "atoy", "toy", "toytoy", and "Nene" can be "ineng," "neng", or "nini".

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