Whenever the author and playwright Samantha Ellis tries to define her heritage to people, she often finds them correcting her. “So many times I’ve said I’m an Iraqi Jew and been… told ‘you mean you’re mixed’ or ‘which parent is which?’ or just ‘how weird’,” she writes in her richly detailed memoir, in which she explores the complex, centuries-old history of the Iraqi-Jewish community and its vanishing language, Judeo-Iraqi Arabic.

The daughter of Iraqi-Jewish refugees who came separately to London with their families during periods of persecution for the community in Baghdad, Ellis is moved to seek out stories, expressions and objects that will fill some of the gaps in that history when she realises that she lacks the vocabulary to pass on the language of her childhood to her own young son. It’s a quest in which intensely personal family memories come to represent the enormity of what has been lost by an entire people (at the time of writing her preface, the Jewish community still living in Iraq numbered three).

Ellis writes that she has no idea what her father looked like as a child; he has no photographs from his first decade because, when his family left Baghdad in 1951, Jews were only permitted one small suitcase each, with strictly delimited contents. She interviews both her parents and her ninetysomething grandmother, Aida, about Jewish life in Baghdad and the trauma of leaving. Aida lived through the 1941 pogrom known as the Farhud, when more than 200 Jews were murdered in one night and Aida’s family were saved by their Muslim neighbours. To piece together a bigger picture, however, Ellis has to search further afield, where she finds the evidence scant.

Everywhere she looks she sees ghosts of what has been lost. There is little surviving literature in Judeo-Iraqi Arabic (“My language was not like Yiddish, which was saved by its books”) and few artefacts in the British Museum, despite the number of Iraqi antiquities plundered by the British in the 1920s and 30s. When she tries to use the kohl in the little pots her mother brought from Baghdad in the 1970s, she finds it has all dried up. Nor will she ever eat the traditional fish dish masgouf, because it has to be made with a particular type of carp only found in the Tigris; a fish now tainted because it was found that the carp had been feeding on the corpses of torture victims thrown into the river under Saddam Hussein’s regime. Her own paternal family name is gone, anglicised from “Elias”.

Over and above these small losses arches the greatest loss of all: the permanent loss of homeland. Ellis and her family have little hope of returning to Iraq as it’s now a death penalty offence to have any association with Israel – an edict that effectively bars most of the Jewish diaspora. “Maybe I could go to Iraq and escape death,” she writes, “but I couldn’t go to Iraq and feel safe.”

Yet, despite this litany of loss, persecution and violence, Chopping Onions on My Heart (the Judeo-Iraqi Arabic equivalent of “rubbing salt in the wound”) is an optimistic and often wryly funny book. It’s an exploration of collective memory: how we choose what to value and what to pass on to our children. Ellis is a knowledgable and entertaining guide to the history of a community that “rarely made it into history books” but whose story is an integral part of the broader history of the Middle East, reverberating down to the present.

Her celebration of her endangered culture – through food, art, song, and especially language – culminates in the conclusion that changing identities can be reframed as addition and evolution rather than loss. Watching her son eat makhboose (traditional date-stuffed pastries), she says: “I felt I’d brought there and then into here and now not as trauma or anxiety, but as a mnemonic to help us remember happiness. A gift from our affectionate ghosts.” This book is likewise a gift to the future, rich with insights about the nature of belonging that are not limited to one community but matter to all of us.

• Chopping Onions on My Heart by Samantha Ellis is published by Chatto & Windus (£16.99). To support the Guardian and Observer order your copy at guardianbookshop.com. Delivery charges may apply